The present invention relates to connection devices which are connected to the pairs of a multipair cable for transmitting high-frequency signals and which include means for compensating crosstalk between the pairs to be connected and other pairs.
Connection devices of the above kind include contact members which are arranged side by side in a row and to which the insulated wires of the pairs of the cable are connected. To connect them to the contact members, the pairs of insulated wires are exposed by stripping the sheath from the end part of the cable and untwisted. The proximity and parallel relationship of the various pairs of insulated wires in the end part of the cable when the sheath has been removed and they have been untwisted, and the proximity of the contact members in the row, give rise to problems of crosstalk between adjacent pairs which limit the frequencies that can be used for transmission over the pairs.
The document DE-C1-196 49 668 discloses a male connector of the above kind fitted to a cable with four individually screened pairs.
The connector has a row of eight adjacent contact members and a flat wiring support for the pairs and the insulated wires of the pairs. The wiring support has a rear part for holding the pairs, a front part for guiding or connecting the insulated wires and an intermediate or crossover part.
The intermediate part carries separators which divide it into four parallel channels. The end pairs of insulated wires received on it are each guided in one of the end channels and are screened practically as far as the front connecting part. The two insulated wires of each pair that has been removed from its screen are connected to two contact members at one end of the row. The two middle pairs that are received on the intermediate part are then freed from their individual screens. Their insulated wires are guided in the two channels and cross over so that each of the two middle channels contains two insulated wires each belonging to one of the two middle pairs, which provides coupling compensation along the middle channels. The insulated wires terminate in the connection part, where they are connected to the four middle contact members of the row in a required order that is different from their original order.
The above connector is relatively complex. It exploits the features of the screened pair cable to which it is fitted, but a screened-pair cable is very costly compared to a cable with unscreened pairs. Mounting the connector on a screened-pair cable is difficult and takes a particularly long time.
The document U.S. Pat. No. 5 556 307 discloses a female connection device fitted to the end of a multipair cable. The female connection device comprises a female connector at the front and a module at the rear for compensating coupling between pairs in the female connector at the front.
The female connector contains a row of curved flexible conductive inserts which are accessible through a front opening, into which a complementary male connector is plugged, and retained in a rear part of the female connector. It also includes a row of flat insulation displacement contacts with first ends connected to the conductive inserts in the rear part of the female connector and second ends projecting out of that rear part.
The coupling compensator module at the rear is mounted directly on the cable and is clipped to the rear part of the female connector. It comprises two similar parts which are fastened together and between which are defined, in succession, a rear cable entry and cable retainer, a rear row of channels for separating the insulated wires of the various pairs of the cable and keeping them flat, a cavity in which the insulated wires cross over and a front row of channels for guiding the wires and connecting them to the insulation-displacement contacts. The connecting channels are slotted at each end of their length for inserting insulation displacement contacts and the rear module clips onto the front female connector. The channels of the rear row, and therefore the insulated wires present in them, on the upstream side of the crossover cavity, are of particular length in order to compensate coupling between the parallel transmission paths defined downstream of the crossovers by the insulation displacement contacts and the conductive inserts of the female connector, which are connected to one another and to the pairs of the cable.
The above female connection device uses very short conductive inserts in the front female connector part, which reduces commensurately the coupling to be compensated. However, it uses insulation displacement contacts for connecting the pairs of insulated wires to the conductive inserts. The insulation displacement contacts, which are parallel to one another and face-to-face in their row, considerably increase the coupling to be compensated in said rear row of channels and limit the accuracy of the balancing that the compensation to be applied seeks to achieve. It further produces areas in which the characteristic impedance of the pairs is subject to a sharp discontinuity, which combines with a sharp discontinuity in the characteristic impedance caused by the conductive inserts and due to the separation of the insulated wires of the pairs along the compensator module and the predetermined but relatively great length required for the rear row of channels. What is more, the insulation displacement contacts are connected to the insulated wires in the connection channels of the coupling compensator module parallel to the insulated wires, which requires a very high insertion force, makes it somewhat difficult to clip the rear module to the front female connector, and entails the risk of the insulated wires slipping in the connecting channels and/or incorrect connection of the wires to the insulation displacement contacts. This method of connecting insulation displacement contacts to the insulated wires rules out the use of multistrand insulated wires.
The object of the present invention is to overcome the drawbacks of the aforementioned prior art connection devices, to improve crosstalk compensation and to reduce harmful effects.
The invention provides a low crosstalk connection device for a multipair cable, the device comprising a stripped end part of said cable, an insulative body, a row of first contacts mounted in said body, rear support means along said stripped end part of said cable including a row of parallel channels of particular length for retaining insulated wires of said pairs, front support means for guiding said wires, at the same pitch as said contacts and in a particular order different from that of said wires in said channels, for connecting said wires to said first contacts, and an intermediate part in which the insulated wires of said pairs cross over, wherein said channels are in lateral communication with one another along their length and define a peripherally closed passage for tightly gripping all of said insulated wires in contact with one another in a layer, near the end of the sheath of said cable, and wherein said front support means include a path for transversely connecting said wires to said first contacts.
Advantageously:
The rear support means comprise a block through which said channels pass and which is held in position relative to said front support means.
The intermediate part between said front and rear parts for holding the crossing over wires fixed in position thereon is of limited length.
Said front and rear support means and said intermediate part are each less than 5 mm long.
Said front and rear support means form a common support equipped with said block and integrating said intermediate part in which said insulated wires cross over.
Said device constitutes a male RJ45 connector and said support is mounted in said insulative body constituting the connector body.
Said device is a terminal strip in which said insulative body is that of said terminal strip and one face of said insulative body of which constitutes said intermediate part and said front support means and holds said block in position on it.
Said device is a first cross-connection connector in which said insulative body is that of said first cross-connection connector and consists of said support and a cover which can be attached to it.
Said device is a second cross-connection connector in which said insulative body is that of said second cross-connection connector, said front support means for guiding said wires is a rear part of said insulative body and an overall protective member fastens said rear block and said insulative body together and extends onto said sheathed cable.